Comment 2 for bug 1427944

Reviewed: https://review.openstack.org/161069
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=5d8eb7184ebcf0a1ad245de28d6405bda385b680
Submitter: Jenkins
Branch: master

commit 5d8eb7184ebcf0a1ad245de28d6405bda385b680
Author: Joe Cropper <email address hidden>
Date: Tue Mar 3 19:46:21 2015 -0600

    Nil out inst.host and inst.node when build fails

    This patch addresses a bug that leaves instance.host/node set after
    a VM fails to build or reschedule (e.g., due to an error in the spawn
    path). Rather, we should nil these out at the end of the build
    process so that the instance is not erroneously being associated
    with stale host/node information.

    Also included are a few cosmetic updates in comments and eliminating
    some implied 'None' parameters from "dict.get(key, None)" calls I
    found during the course of investigating this change.

    Change-Id: I4d9c90b1d3fcce5237323fffcc6db1fb93d23e37
    Closes-Bug: #1427944